The present invention relates generally to an apparatus for controlling the temperature and flow of liquids, and in one instance, controlling cleaning liquid flow in a manual or soak parts washer apparatus of the type having a cleaning liquid reservoir, a receptacle, such as a sink, associated with the reservoir for positioning parts to be washed by cleaning liquid contained in the reservoir, a heating element for adjusting the temperature of the cleaning liquid and a pump and motor for recirculating the cleaning liquid from the reservoir to the sink.
Typical parts washers with which the invention is useful are parts washers of the type described in U.S. Pat. Nos. 3,522,814; 4,049,551; 4,261,378; 5,598,861 and 5,720,308, each of which is incorporated by reference in their entireties herein. These patents generally describe parts washers wherein a sink is positioned atop a barrel-type reservoir and in which a submersible pump in the reservoir circulates cleaning liquid from the reservoir to the interior of a sink in which parts are disposed for washing. While the washing is being carried out, cleaning liquid continually drains from an opening in the bottom of the sink back into the reservoir sometimes passing through a filter or screen on its way to the reservoir.
Over the years, the most successful parts washers have been those that can be readily and economically serviced. Servicing has consisted of changing the cleaning liquid, the filter, if any, and a general machine clean-up. In use, cleaning liquid used in a parts washer becomes increasingly dirty until its ability to clean is compromised by the presence of dispersed contaminants and/or soluble oils and greases. Service may also include replacing the entire heater/pump module as a result of operational failure.
The present invention involves the discovery that earlier parts washers, however successful, have several disadvantages. First, the parts washers are not field serviceable. If one component of the temperature and/or pump control assembly fails, the entire unit must be replaced. For example, the pump is the source of a majority of problems related to operability. The pump housings are usually plastic and commonly attached to a distal end of a conduit used to route power control wires for the pump motor. A metallic fitting interfaces the conduit to the pump housing. Cracks develop in the pump housing at the interface as a result of pump vibrations because the pump is not additionally supported. As a result of this disadvantage, the pump often fails and the entire unit must be replaced. Consequently, costs to the vendor and ultimately the customer are constantly increased.
Another disadvantage of earlier parts washers is that there is no ability to interactively troubleshoot or diagnose problems with respect to the operative condition of the parts washers. In this respect, there was no diagnostic readout. Manual piece-by-piece diagnosis was necessary in order to determine the reason for inoperability. In some earlier parts washers, a low liquid level shut-off is provided. However, such output has limited usefulness. As a result, field service personnel must replace the entire unit if it is inoperable. Again, costs continue to increase.
Yet another disadvantage of earlier parts washers is that there is no adjustable temperature controller for use with various different cleaning liquid requirements. Conventional temperature controls are usually simplistic bi-metallic switches which are subject to short to ground failure in the event the electrical control wire conduit is breached and cleaning liquid becomes disposed therein. Further, these switches are pre-set from the manufacturer for a specific temperature set-point which cannot be adjusted. A different switch, hence a different unit, may be required for various different cleaning liquids. Moreover, the control accuracy of the switches is very low, normally on the order of plus or minus 5–15 degree temperature variance from the set-point permitted. As a result, costs to the vendor and customer are increased and the customer experiences inaccurate temperature control and cleaning liquid performance.
Still another disadvantage of the earlier parts washers is that they are large, unwieldy and generally very difficult to handle. There is no structure provided for properly lifting the heater/pump module. As a result, the units are mishandled and easily damaged during routine servicing.
A further disadvantage of earlier parts washers is that there is no over-current protection for the unit. This is especially detrimental to the long-term operation of the unit when operators do not pre-qualify electrical service outlets to which the units are connected.
Therefore, there is a need for a parts washer having an improved temperature and pump control that is modular in design to facilitate field reparability, provides the ability for diagnosis and trouble-shooting, includes an adjustable and programmable temperature controller, is made of durable materials and provides an information readout.